Joint application of an empirical and mechanistic model for regional lake acidification

The empirical direct distribution model for lake acidification is calibrated for use in an integrated assessment model which predicts the regional impact of an acid deposition control strategy. The calibration is based on the mechanistic Model of Acidification of Groundwater in Catchments (MAGIC). The models are applied jointly to a set of 33 statistically-selected lakes in the Adirondack region of New York. Calibration of the direct distribution model is based on a step-function application of acid deposition to MAGIC. Comparative evaluations of the resulting model predictions are made using historic deposition estimates and two alternative future deposition scenarios. The predictions of the direct distribution model match well the shapes and patterns of change of the regional distributions of ANC and pH predicted by MAGIC, the short- and medium-term dynamics of these changes, and the effect of including organic acids. However, small, long-term decreases in the fraction of incoming acid deposition neutralized by lakes and their watersheds predicted by MAGIC are not reproduced.     

Population monitoring for genetic damage induced by environmental physical and chemical agents

The short-term tests performed in vitro on different systems, from phage to human cells, or in vivo, on laboratory animals, allow only a qualitative estimate of the action of mutagenic agents, and the extrapolation of such experimental results to man may encounter many difficulties.Direct biomonitoring of populations exposed to chemicals could represent a more realistic approach for an evaluation of the hazards to man. Certain methods are still under development. Nevertheless, other ones can already by used routinely, e.g. the cytogenetic observations on peripheral blood lymphocytes and the Ames test for mutagenic substances in urine, and can provide useful suggestions how to set threshold limits for chemical substances encountered in the working environment.     

Solid Absorbent Method for Sampling and Analysis of Nitrogen Dioxide in Ambient Air

A sampling and analysis system was developed for measuring concentrations of nitrogen dioxide in ambient air. Copper shot was found to be an effective absorbent for collecting samples at ambient levels. The analytical system was based on the desorption of the sample from the copper by heating in a hydrogen carrier stream. The desorbed sample was then determined by a combination of catalytic pyrolysis, which converted it to ammonia, and a Coulson Conductivity Detector. Data are presented showing overall recovery, effects of storage of collected samples, results for 24-hour sampling and interferences. Studies indicated the feasibility of the method for short time sampling as well as for 24-hour sampling periods. The detection limit was shown to be as little as 100 ng NO₂ in laboratory studies. This solid absorbent method provides a simple, convenient, and compact means for air sampling.     

Investigating soils retention ratios and modelling geochemical factors affecting heavy metals retention in soils in a tropical urban watershed

This study aimed at investigating the retention of Pb and Cd in soils and the geochemical factors influencing the adsorption of these pollutants. Soil samples were air-dried and ground to pass through a 2-mm sieve, and different soil extracts were prepared for chemical analysis (organic matter, cation exchange capacity and pH). Total Pb and Cd were extracted with diacid using digestion method and determined by atomic adsorption spectrophotometer (AAS) after filtration. Results revealed that the heavy metals retention ratio (RR) of the Rhodic ferralsol, Xanthic ferralsol and Mollic gleysol (2) were very high for Cd (>80 %) and was relatively low (generally < 60 %) for Pb. In contrast, RRs for the Plinthic gleysol and the Mollic gleysol (1) were relatively low (<60 %), regardless of the heavy metal concerned. Multiple regression equations indicated for Pb and Cd concentrations different linear relationships over simple linear regression, when pH, organic matter, clay percentage and cation exchange capacity (CEC) were used as independent variables. Results indicate that organic matter exerts major influences on the retention of Pb and Cd in soils, while CEC, clay content and pH have a minor influence in this process in the Ntem watershed. From these observations, the application of soil organic matter could be a solution in protecting shallow aquifers from heavy metal pollution and thus insuring that they are not a hazard to public health.     

Accounting for human behavior,local conditions and organizational constraints in humanitarian development models

The current trend in foreign aid is toward small-scale sustainable development projects in partnership with defined communities. However, these projects are subject to the influences of self-interested human behavior, poorly defined community structures and resources and organizational constraints that can prevent full realization of development models. Under these constraints, attempting participatory community development models to the exclusion of other techniques may not be the most effective way to achieve positive change. Instead, development agencies should consider adopting other proven elements of development in combination with the spirit of community development to achieve a positive impact within the community and organizational structures and ensure accountability for success. A small-scale attempted, sustainable development case study in Rwanda is reviewed, as well as a new concept for larger scale development integrating ‘carbon credits’. Additionally, a development accreditation organization is proposed to ensure additional accountability in this field.     

Assessment of ecotoxicological risks related to depositing dredged materials from canals in northern France on soil

The implementation of an ecological risk assessment framework is presented for dredged material deposits on soil close to a canal and groundwater, and tested with sediment samples from canals in northern France. This framework includes two steps: a simplified risk assessment based on contaminant concentrations and a detailed risk assessment based on toxicity bioassays and column leaching tests. The tested framework includes three related assumptions: (a) effects on plants (Lolium perenne L.), (b) effects on aquatic organisms (Escherichia coli, Pseudokirchneriella subcapitata, Ceriodaphnia dubia, and Xenopus laevis) and (c) effects on groundwater contamination. Several exposure conditions were tested using standardised bioassays. According to the specific dredged material tested, the three assumptions were more or less discriminatory, soil and groundwater pollution being the most sensitive. Several aspects of the assessment procedure must now be improved, in particular assessment endpoint design for risks to ecosystems (e.g., integration of pollutant bioaccumulation), bioassay protocols and column leaching test design.     

Gaseous emissions from weaned pigs raised on different floor systems

Gaseous emissions from agriculture contribute to a number of environmental effects. Carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) are greenhouse gases taking part to the global problem of climate change. Ammonia (NH₃) emissions are responsible of soil acidification and eutrophication and contribute also to indirect emissions of N₂O. This work evaluated the influence of the type of floor on the emissions of these gases in the raising of weaned pigs. Two trials were carried out. In the first trial, the animals were kept either on fully slatted floor or on straw-based deep litter and, in the second one, either on fully slatted floor or on sawdust-based deep litter. For each trial and on each type of floor, 2 successive batches of weaned pigs were raised without changing the litter or emptying the slurry pit between the 2 batches. The rooms were automatically ventilated to maintain a constant ambient temperature.The performance of the animals was not significantly different according to the floor type. In trial 1, the nitrogen contents of the straw deep litter (including the substrate) and slurry were respectively 276 and 389 g pig⁻¹. In trial 2, the sawdust deep litter and slurry nitrogen contents were respectively 122 and 318 g pig⁻¹.Raising pigs on straw deep litter produced proportionately around 100% more NH₃ than raising pigs on slatted floor (0.61 g NH₃-N d⁻¹ pig⁻¹ vs. 0.31 g NH₃-N d⁻¹ pig⁻¹; P < 0.05). Differences in CO₂, H₂O and CH₄ emissions were not significant between systems. Raising pigs on sawdust deep litter produced also proportionately more NH₃ (+52%; 0.55 g NH₃-N d⁻¹ pig⁻¹ vs. 0.36 g NH₃-N d⁻¹ pig⁻¹; P < 0.01) but also more CO₂ (+25%; 427 g d⁻¹ pig⁻¹ vs. 341 g d⁻¹ pig⁻¹; P < 0.001) and H₂O (+65%; 981 g d⁻¹ pig⁻¹ vs. 593 g d⁻¹ pig⁻¹; P < 0.001) and less CH₄ (−40%; 0.52 g d⁻¹ pig⁻¹ vs. 0.86 g d⁻¹ pig⁻¹; P < 0.001) than raising pigs on slatted floor. Practically no N₂O emission was observed from rooms with slatted floor while the N₂O emissions were 0.03 and 0.32 g N₂O-N d⁻¹ pig⁻¹ for the straw and sawdust deep litter respectively. The warming potential of the greenhouse gases (N₂O + CH₄), were about 22, 34 and 168 g CO₂ equivalents per day and per pig on fully slatted floor, straw or sawdust deep litter respectively.In conclusion, pollutant gas emissions from rearing of weaned pig seem lower with fully slatted plastic floor system than with deep litter systems.